Method for multimedia flow transport

ABSTRACT

A method and system for transferring to a same client terminal at least a first flow with a first service quality and at least a second flow with a second service quality. The first flow is transmitted to the client terminal through an unconnected network, and the second flow is transmitted to the client terminal by a content server through a connected network after network resource booking with service quality by exchanging messages via the unconnected network. The method establishes a high throughput link between the client terminal and the content server, and transmits the second flow with the booked service quality to the client terminal through the high throughput link.

TECHNICAL FIELD

The present invention is located within the field of transferring dataflows through a data exchange network and is more specifically relatedto a method and a system for transferring at least two data flows withdifferent service quality (Qos) requirements to a same terminal.

STATE OF THE PRIOR ART

The mechanism for transferring and switching data flows, such as IPflows, is based on the routing principle.

A router is an interface between two networks which may use differentprotocols, for letting flows pass through it, either native IP orencapsulated in another protocol such as ATM (Asynchronous TransferMode), for example. The routing is generally based on analyzing theheader of the packets to be transferred.

Let us recall that for performing the routing of packets in a meshnetwork, a node should know the state of all the other nodes beforedeciding or sending a packet. This cannot be achieved presently. Also,as a first step, the routing is supported by several components amongwhich are a packet switch and a routing table. A switching node isgenerally formed with output lines which transmit frames obtained frompackets. The packets are routed by the switch towards an output linefrom the routing table.

In a known art, the routing may be performed in a centralized way from acentral node which makes the decision relatively to the definition of anew routing table and to its sending to the different network stations.This central node receives information from all the components of thenetwork and designs its routing table according to algorithms determinedbeforehand. Among the items which may be taken into account to establishthis new routing table, let us mention:

-   -   the cost of the links;    -   the cost of passing in a node;    -   the requested throughput;    -   the requested transit delay;    -   the number of nodes to be crossed;    -   the transfer security for certain classes of packets;    -   the occupation of the switching node's memories;    -   the occupation of the line couplers.

Let us also mentioned the so-called fixed routing in which the routingtable does not vary over time. This routing consists of sending eachpacket entering the node in the same direction generally correspondingto the shortest route algorithm.

A more developed technique consists of sending routing tablesasynchronously.

Another known principle, MPLS (MultiProtocol Label Switching) enables IPflows to transit in different directions by means of overencapsulationof the same packets. With this, the flows may be classified so as totransfer them on networks with different service quality (QoS) withoutchanging the principles of the routers and the routing mechanisms used.

It appears that with the techniques described above, it is not possibleto direct IP packets with different service qualities in a network ofstandard pieces of equipment, unless the destination addresses of thesepackets are broadcasted for example with a protocol of the ProtocolIndex Multicast type, in which the broadcast addresses belong to afamily of predetermined addresses. As a result, the routing is onlypossible for addresses known beforehand.

This is not compatible with multicast mode data transmission towards aplurality of terminals.

More specifically, the broadcast of addresses is not adapted to thedistribution of data or audiovisual programs through an open networksuch as the Internet network.

French patent application No. 99 1352, filed by the applicant on Oct. 4,1999, describes a protocol with which a calling terminal may booknetwork resources with service quality through an unconnected network inorder to establish a connection through a connected network with acalled terminal.

The invention described in this application is limited to the resourcebooking GSMP (Generic Switch Management Protocol) and P1520 protocolsdescribed in the article “IEEE, p-1520 Standards Initiative forProgrammable Network Interface”, IEEE Communications Magazine, vol. 36,No. 10, pp. 64-70, October 1998, published by J. BISWAS, A A. LAZAR, J.F. HUARD, K. S. LIM, S. MAHJOUB, L. F. PAU, M. SUZIKI, S. TORTENSSON, W.WANG and S. WEISTEIN. Consequently, the invention is solely applied toATM flows transported on a connected mode ATM network. Moreover, themethod described in this application does not provide transparentmultiplexing of flows with different service qualities.

The object of the invention is to overcome the insufficiencies of theprior art described above by means of a method and of a system enablingIP data flows from at least two different pieces of equipment withdifferent service quality requirements towards a same terminal.

Another object of the invention is to combine a protocol of a connectednetwork and a protocol of an unconnected network to transfer digitaldata with high throughput towards a same client terminal.

Another object of the invention is to distribute said data through atelephone line by using sXDL technology.

DISCLOSURE OF THE INVENTION

The invention therefore provides a method for transferring to a sameclient terminal, at least a first flow with a first service quality andat least a second flow with a second service quality, said first flowbeing transmitted to the client terminal through an unconnected network,and said second flow being transmitted to said client terminal by acontent server through a connected network, after network resourcebooking with service quality by exchanging messages via the unconnectednetwork.

The method according to the invention further includes the followingsteps:

-   -   establishing a high throughput link between the client terminal        and the content server;    -   multiplexing the first and second flow into a same flow;    -   transmitting the multiplex obtained at the client terminal        through said high throughput link.

According to the invention, said high throughput link is of the xDSLtype.

In a particular application of the method according to the invention,the second flow represents audiovisual data and the first flowrepresents signals for controlling the second flow.

According to a preferred embodiment of the invention, the unconnectednetwork is the Internet network and the connected network is an ATM(Asynchronous Transfer Mode) network.

In this case, the method further includes a step consisting of sendingat least one external command to the ATM network from a network controlplatform in order to establish the high throughput link between thecontent server and the client terminal. The first flow and the secondflow are multiplexed into a same flow and transmitted to the clientterminal via the established high throughput connection.

In the preferred embodiment, several terminals request audiovisual data,within the framework of a VoD (Video On Demand) application for example,the transmission of the audiovisual flows towards a client terminalincludes the following steps:

-   -   connecting the client terminal to a service platform via the        Internet network for requesting the audiovisual contents:    -   identifying the server of the audiovisual contents;    -   booking through a control platform, network resources with the        predetermined service quality between the audiovisual server and        the client terminal;    -   activating a point-to-point (PPP) (Point to Point Protocol)        session between said audiovisual server and the client terminal        with the service quality (QoS) established previously;    -   broadcasting said audiovisual contents with the associated        control (reading, pause, backward . . . ) signals to the client        terminal through the ATM network.

The invention also relates to a system for transferring to a same clientterminal at least a first flow with a first service quality and at leasta second flow with a second service quality, said first flow beingtransmitted to the client terminal through an unconnected network, andsaid second flow being transmitted to said client terminal by a contentserver through a connected network after network resource booking withservice quality by exchanging messages via the unconnected network.

The system according to the invention includes:

-   -   means for establishing a high throughput link between the client        terminal and the content server;    -   means for multiplexing the first and second flow into a same        flow;    -   means for transmitting the multiplex obtained at the client        terminal through said high throughput link.

In a preferred embodiment of the invention, said means for establishinga high throughput link between the client terminal and the contentserver include a digital multiplexer of the DSLAM (Digital SubscriberLine Access Multiplexer) type and at least one ATM switch for connectingthe client terminal to the content server.

The system according to the invention further includes a first highthroughput BAS (Broadband Access Server) server for providing a highthroughput link via the Internet network between the ATM network and acontrol network, and a second high throughput BAS server for providing ahigh throughput link between the client terminal and an audiovisual dataserver.

SHORT DESCRIPTION OF THE DRAWINGS

Others features and advantages of the invention will be apparent fromthe description which follows, taken by way of a non-limiting example,with reference to the appended figures wherein:

FIG. 1 schematically illustrates a system for transferring data flows toa client terminal according to the invention from a content server.

FIG. 2 schematically illustrates a distribution of content servers bygeographic zones.

FIG. 3 illustrates a partial functional diagram of a preferredembodiment of the method according to the invention.

DETAILED DISCLOSURE OF SPECIFIC EMBODIMENTS

The following description relates to a specific exemplary application ofthe invention consisting of combining the ATM (Asynchronous TransferMode) protocol and the IP protocol (Internet Protocol) in order todesign a VoD (Video on Demand) application which receives requests fordistributing films sent by client terminals through the Internet networkand which sends back to the requesters the audiovisual data encapsulatedin a flow with service quality through an ATM network.

With reference to FIG. 1, a client terminal 2 provided with a modem 4 isable to be connected through the system according to the invention to avideo server 6 among a plurality of geographically distributed videoservers.

As schematically illustrated by FIG. 2, the audio visual programs may bestored in a central data base 7 accessible to different content serversvia a broadband network 3.

The system of FIG. 1 includes a digital multiplexer 8 of the DSLAM(Digital Subscriber Line Access Multiplexer) type, laid out between themodem 4 and a first ATM switch 10. A second ATM switch 12 is connectedto the first ATM switch 10, to a first broadband BAS (Broadband AccessServer) server 14 and to a second broadband server 16, respectively. Thefirst broadband server 14 is connected via the Internet network 20 to aservice platform 22 which communicates with a control platform 24 ableto send network commands to the first switch ATM 10, to the second ATMswitch 12, to the first broadband BAS (Broadband Access Server) server14 and to a second broadband server 16.

The method for transferring to the client server 2 the audiovisual flowwith service quality will be described with reference to FIG. 3, whereinthe different steps of the method are illustrated by arrows connectingthe different pieces of equipment of the system.

In step 30, the requester of an audiovisual program sends a standardrequest for connecting to the service platform 22 via the Internetnetwork 20.

After authentication and localization of the client by the serviceplatform 22 via the control platform 24, the service platform 22identifies the proximity video server 6 of the client among thedistributed content servers 6.

In an alternative embodiment, if the audiovisual content desired by theclient is not found on an identified proximity server, the controlplatform 24 dynamically creates a high throughput link between the database 7 and the proximity server 6 through the broadband network 3. Instep 32, the service platform 22 accesses the control platform 24 whichsends to the first ATM switch 10 (step 34), external commands(establishment/release of an ATM connection) for reserving the networkresources with the service quality required for the requested servicebetween the client terminal 2 and the video server 6. The procedure forbooking network resources is described in detail in French patentapplication No. 99 12352, filed by the applicant on Oct. 4, 1999.

In step 36, the control platform 24 activates a service session (PPP)between the client terminal 2 and the first broadband BAS server 14dedicated to video. This session (PPP) is based on the connection withQoS established in step 34.

In step 40, the service platform 22 starts the video application at theclient and controls the broadcasting of the flow of audiovisual datawith the booked service quality.

The video channel with the thereby created QoS is used for transferringthe multimedia flow towards the client terminal 2 through the digitalmultiplexer 8 on the one hand, and on the other hand, for exchangingwith the same client terminal 2, signals for controlling the multimediaflow such as read, pause, fast forward, fast backward and stop commands.

1. A method for transferring a first flow with a first service qualityand a second flow transmitted with a second service quality, comprising:reserving network resources of a predetermined service quality byexchanging messages via a connectionless network protocol over aconnectionless network; selecting a proximity server among a pluralityof content servers after localization of a client terminal; establishinga high throughput, connection oriented link in accordance with thenetwork resources reserved by utilization of the connectionless networkprotocol between the client terminal and the proximity server;multiplexing the first and the second flows into a same flow, whereinthe first flow is transmitted at least in part via the connectionlessnetwork and comprises multimedia control signals distinct from themessages reserving network resources; and transmitting the multiplexedsame flow to the client terminal through the high throughput, connectionoriented link.
 2. The method according to claim 1, wherein the highthroughput, connection oriented link is of xDSL type.
 3. The methodaccording to claim 2, wherein the second flow represents audiovisualdata and the multimedia control signals comprise signals for controllingthe second flow.
 4. The method according to claim 3, further comprising:connecting the client terminal to a service platform via the Internetnetwork for requesting the audiovisual data; identifying the contentserver; booking, through a control platform, network resources with apredetermined service quality between the content server and the clientterminal; activating a point-to-point session between the content serverand the client terminal with the service quality established previously;and broadcasting contents with associated signaling signals to theclient terminal through an ATM network.
 5. A system for transferring afirst flow with a first service quality and a second flow transmittedwith a second service quality, comprising: means for reserving networkresources of a predetermined service quality by exchanging messages viaa connectionless network protocol over a connectionless network; meansfor selecting a proximity server among a plurality of content serversafter localization of a client terminal; means for establishing a highthroughput, connection oriented link in accordance with the networkresources reserved by utilization of the connectionless network protocolbetween the client terminal and the proximity server; means formultiplexing the first and the second flows into a same flow, whereinthe first flow is transmitted at least in part via the connectionlessnetwork and comprises multimedia control signals distinct from themessages reserving network resources; and means for transmitting themultiplexed same flow to the client terminal through the highthroughput, connection oriented link.
 6. The system according to claim5, wherein the high throughput, connection oriented link is of xDSLtype.
 7. The system according to claim 6, wherein the second flowrepresents audiovisual data.
 8. The system according to claim 6, whereinthe means for establishing an xDSL link between the client terminal andthe content server includes a digital multiplexer of DSLAM type and atleast a first ATM switch for connecting the client terminal to thecontent server.
 9. The system according to claim 8, further comprising afirst high throughput Broadband Access Server (BAS) configured toprovide a high throughput link via Internet network between the ATMnetwork and a control network, and a second high throughput BASconfigured to provide a high throughput link between the client terminaland a server of audiovisual data.